Osamu Dazai, one of the most prominent Japanese writers is known for his introspective writing style and existential angst. No Longer Human which means 'Disqualified as a human being' is a Japanese modern fiction published in 1948. It is considered as the final work of Osamu Dazai before his suicide. The work depicts Dazai's own life through the eyes of protagonist Oba Yozo. Dazai's works often explores the themes of human suffering, isolation, identity crisis and sense of despair. Dazai shows strong inclination towards existentialist and nihilist explication of human suffering. The novel is powerful exploration of an individual's existential crisis. It traces Yozo's development of experiences and his perception from his childhood to adulthood. Keywords: No Longer Human, identity crisis, Dazai, existentialism, nihilism, death.